Abstract
Aminoacetone synthetase from beef liver mitochondria was purified to homogeneity and shown to be a member of the pyridoxal 5'-phosphate-dependent family of enzymes. This enzyme catalyzes the condensation of glycine and acetyl-CoA to produce CO2, CoA, and the stable product aminoacetone. Bovine aminoacetone synthetase is a dimer (Mr 56,000) of identical subunits and contains 2 mol of pyridoxal phosphate/mol of dimer. The holoenzyme was resolved by dialysis against cysteine and has a pI of 5.2. The holoenzyme shows an absorption maximum at 428 nm which undergoes a shift to 335 nm when reduced with sodium borohydride. The Km values of glycine and acetyl-CoA were 22 mM and 53 microM, respectively. Initial velocity studies indicate that the condensation reaction proceeds by an ordered mechanism. With the exception of aminomalonate, bovine aminoacetone synthetase acts specifically on glycine and acetyl-CoA. Coupled reactions of purified bovine aminoacetone synthetase and porcine L-threonine dehydrogenase demonstrated the interconversion of threonine and glycine.
Highlights
Aminoacetone synthetase from beef liver mitochon- tion as 2-amino-3-oxobutyrate-ColAigase, has been imdria was purified to homogeneity and shown to be a plicated in the catabolism of threonine to form glycine and member of the pyridoxal 5”phosphate-dependent famac-etyl-coA
To verify the identity of the final product as aminoacetone, pyrroles formed from terminated incubations were extracted with ethyl acetate and applied to silica gel thin layer chromatography (TLC) plates along with pyrrole prepared from an aminoacetone standard
+ stated above.Beef liver mitochondria were prepared according The molecular weight of aminoacetone synthetase was esto modified method of Schneider and Hogehoom (1950)
Summary
The ammonium salt of aminomalonate was prepared according to the method of Thanassi (1970); 3-acetyl-2,5-dimethyIpyrrole (aminoacetone pyrrole) by the procedure of Urata and Granick (1963); aminoacetone HCl following a modified procedure of Hepworth (1973); and ethyl acetoacetate pyrrole of aminoacetone according to the procedure of Matthew and Neuberger (1963). This enzyme was isolated from porcine liver according tothe method of Tressel et aL2.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
